Shaft coupling mechanism

ABSTRACT

Mechanism for coupling an externally splined power take-off shaft with a hollow internally splined shaft, comprising a plurality of locking elements radially movable between inner locking and outer unlocking positions within a like plurality of circumferentially spaced apertures in the wall of the hollow shaft, the elements being engageable in the former position with a circumferential groove in the power take-off shaft to lock the shafts against relative axial movement. A retaining member is axially slidable on the periphery of the hollow shaft between a first position wherein it surrounds the locking elements and prevents their disengagement from the groove in the power shaft and a second position wherein the elements are free to move to their unlocking position, the member being biased toward the former position. A latch ring on the hollow shaft is operable to move the retaining member from its first to its second position, and is engageable with a recess in the periphery of the hollow shaft to lock the member in the latter position. As the hollow shaft is inserted onto the power take-off shaft, the latter engages and moves the locking elements radially outwardly against the latch ring, thereby disengaging the ring from the recess in the hollow shaft and permitting the retaining member to move back toward its first position.

[ 51 ,Hu1y24,i973

[ 1 SHAFT COUPLING MECHANISM [7 5] Inventors: Raymond Steele Wilkes,Ottumwa,

lowa; Homer D. Wltzel, Moline, Ill.

[73] Assignee: Deere & Company, Moline, Ill.

[22] Filed: Sept. 15, 1971 [21] App No.: 180,603

Primary Examiner-Charles J. Myhre Assistant Examiner-Randall l-lealdAttorney-H. Vincent'Harsha, William A. Murray sta e-hm [57] ABSTRACTMechanism for coupling an externally splined power take-off shaft with ahollow internally splined shaft, comprising a plurality of lockingelements radially movable between inner locking and outer unlockingpositions within a like plurality of circumferentially spaced aperturesin the wall of the hollow shaft, the elements being engageable in theformer position with a circumferential groove in the power take-offshaft to lock the shafts against relative axial movement. A retainingmember is axially slidable on the periphery of the hollow shaft betweena first position wherein it surrounds the locking elements and preventstheir disengagement from the groove in the power shaft and a secendposition wherein the elements are free to move to their unlockingposition, the member being biased toward the former position. A latchring on the hollow shaft is operable to move the retaining member fromits first to its second position, and is engageable with a recess in theperiphery of the hollow shaft to lock the member in the latter position.As the hollow shaft is inserted onto the power take-off shaft, thelatter engages and moves the locking elements radially outwardly againstthe latch ring, thereby disengaging the ring from the recess in thehollow shaft and permitting the retaining member to move back toward itsfirst position.

PATENTEU SHEEI 1 0f 2 1 N VIEN TORS RAYMOND S. WILKES HOMER D. WITZELATTORN Y I snxrr consume MECHANISM BACKGROUND OF THE INVENTION Thepresent invention relates generally to shaft coupling apparatus of thetype having a plurality of radially movable locking elements in oneshaft engageable with a circumferentail recess in the other shaft, andmore particularly to such apparatus having means facilitating thecoupling of the shafts.

An agricultural tractor conventionally includes an externally splinedpower take-off shaft extending longitudinally from the rear portionthereof, to which is connectible, for powering various towed or rearmounted implements, a power transmission shaft having a hollow,internally splined portion at its forward end. To accommodate relativemovement between the tractor and the implement, the latter shaft isconventionally provided with a universal joint adjacent to each of itsends. Since an exposed, rotating shaft presents a serious safety hazard,substantial efforts have been put forth in the past by those working inthe art to develop suitable shielding for such power transmissionshafts, including shielding for the universal joints included thereon.Some results of these efforts are disclosed in U.S. Pat. Nos. 2,772,550,issued Dec. 4, 1956 to Harrington, 3,357,206, issued Dec. 12, 1967 toChristie, and 3,462,975, issued Aug. 26 1969 to Skromme et al., all ofwhich are assigned to the assignee of the present invention. Theshielding devices disclosed in the latter two patents each include apair of cooperating, bellshaped shields which surround the universaljoint on the forward'end of the power shaft. Although efiective toprevent contact with the universal joint, shielding devices of thistype, when used in combination with a conventional shaft couplingmechanism, also materially increase the effort required to connect thepower shaft to the tractor PTO shaft, and it is thus feared that suchshields will not gain general acceptance and use.

The problems encountered in connecting a shielded shaft to a PTO shaftresult in large part from the apparatus conventionally employed toaxially lock the two shafts together, that apparatus including aplurality of locking elements radially movable in apertures in thehollow portion of the power shaft and engageable in the radial innerposition with a circumferential groove near the outer end of the PTOshaft. A retaining member is employed to maintain the locking elementsin their inner locking position during operation of the shafts, themember being axially movable against the biasing force of a spring topermit the elements to move radially outwardly and thereby release thetwo shafts from their axially locked position. To connect the powershaft with the PTO shaft, the retaining member must thus be held axiallyagainst the biasing force of the spring simultaneously as the splines onthe power shaft are mated with those on the PTO shaft and the powershaft is aligned with and inserted axially on the PTO shaft. Thepresence of a shield enclosing the power shaft and universal jointthereof substantially increases the difficulty of this task.

SUMMARY OF THE INVENTION Accordingly, it is the primary object of thepresent invention to provide apparatus facilitating the task of couplinga shielded power shaft to a tractor PTO shaft. More particularly, it isan object to provide apparatus for locking the retaining member on thepower shaft axially against the force of its biasing spring, therebypermitting insertion of the power shaft on the PTO shaft without thenecessity of simultaneously holding the member against the spring. It isanother object to provide such apparatus having means for releasing theretaining member from its locked position automatically in response toinsertion of the power shaft onto the PTO shaft. It is yet anotherobject to provide such apparatus including a collar on the end of thepower shaft for axially locking the retaining member against the forceof the biasing spring, the collar being rotatably lockable to the shaftwhen the retaining member is axially locked thereon, to facilitatealigning the splines on the power shaft with those on the PTO shaft.

In pursuance of these and other objects, the invention comprises,generally, a latch ring slidably mounted on the power shaft andengageable with the locking element retaining member for moving thelatter against the spring biasing force to a position axially removedfrom the locking elements. Means are provided in the form of a recess inthe periphery of the power shaft en-.

gageableby the latch ring to axially lock the latter, and thereby theretaining member, against the biasing force, and in addition torotatably lock the latch ring to the power shaft. When so locked, thelatch ring extends around the retaining elements in eccentric relationwith the power shaft and is operative to retain at least one of thelocking elements in its inner, locking position. As the power shaft isinserted on the tractor PTO shaft, the

beveled end portion of the latter engages that element and urges itradially outwardly against the latch ring, thereby centering the ring onthe power shaft and disengaging it from the recess therein. When thecircumferential recess in the PTO shaft is aligned with the lockingelements on the power shaft, the retaining member is operative to urgethe elements into engagement with the recess, thereby locking the shaftsagainst relative axial movement.

BRIEF DESCRIPTION OF THE DRAWINGS The preferred embodiment of thepresent invention will be described in conjunction with the accompanyingdrawings in which:

FIG. I is a view of the shaft coupling mechanism of the invention, withportions broken away and in section, showing the shafts in their axiallylocked position;

FIG. 2 is a sectional view taken along the line 2-2 of FIG. I;

FIG. 3 is a sectional view taken along the line 3-3 of FIG. 1;

FIG. 4 is a partial sectional view of the mechanism shown in FIG. II,with the externally splined shaft removed;

FIG. 5 is a view similar to FIG. 4, showing the latch ring and retainingmember axially locked on the internally splined shaft, in preparationfor insertion of the latter on the externally splined shaft;

FIG. 6 is a sectional view taken along the line 6-6 of FIG. 5;

FIG. 7 is a sectional view similar to FIG. 6, but showing the latch ringrotated slightly relative to the internally splined shaft and rotatablylocked thereto; and

FIG. 8 is a view similar to FIGS. 4 and 5, showing the internallysplined shaft partially inserted on the externally splined shaft and thelatch ring and retaining member released from their axially lockedposition.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring first to FIG. 1 of thedrawings, the shaft coupling mechanism of the invention includes anexternally splined shaft which may, for example, comprise the powertake-off shaft of an agricultural tractor, and a mating, internallysplined power transmission shaft 12 of the type conventionally employedto drivingly connect a PTO shaft with a trailing or rear mountedimplement. To accommodate relative movement between the tractor and theimplement, the shaft 12 is provided with a universal joint 14 adjacentto its forward end, the joint 14 comprising a pair of pivotallyinterconnected front and rear yode members 16 and 18, respectively. Therear yoke member 18 is nonrotatably fixed to the forward end of anelongated shaft 20, shown only partially in FIG. 1, while the front yokemember 16 has a forwardly extending hollow hub portion 22 integral withits forward end and internally splined to axially receive the shaft 10.

To guard against accidental contact with the rotating power shaft 12,the latter is provided with safety shielding of the type disclosed inU.S. Pat. No. 3,462,975 issued Aug. 26, 1969 to Skromme et al. andconsisting, generally, of a cylindrical shield 24 for the shaft portion20, and a three-section spherical shield 26 for the universal joint 14.The spherical shield 26 comprises a first bell-shaped member 28rotatably supported on the yoke 18 and extending forwardly over the rearportion of the joint 14, a second bell-shaped member 30 rotatablysupported on the yoke 16 and extending rearwardly over the forwardportion of the joint 14, and a closure member 32'overlapping theadjacent portions of the members 28 and 30 and operative to prevent gapstherebetween when the yokes l6 and 18 pivot relative to each other, asindicated in dashed lines in FIG. 1. The adjacent edges of the shieldmembers 24 and 28 overlap and are commonly axially locked to the yoke 18by means of a plurality of retaining elements 34 slidably received in acircumferential groove 36 formed in the yoke 18; Although axially lockedthereto, the members 24 and 28 are free to rotate relative to the powershaft 12 and thereby perform their protective function. In a likemanner, a plurality of retaining elements 38 slidably received in acircumferential groove 40 formed in the yoke 16 are operative torotatably mount the forward bell-shaped member 30 on the yoke 16 and tonormally prevent relative axial movement therebetween.

The mechanism employed to axially lock the power shaft 12 on the PTOshaft 10 comprises three locking elements or balls 42 received forradial movement in three equally spaced apertures 44 extending throughthe wall of the hub 22. The balls 42 are movable in the apertures 44between a radial outward, unlocking position wherein the hub 22 is freeto move axially on the shaft 10 (see FIG. 8), and a radial inward,locking position wherein the balls 42 are operative to engage acircumferential recess 46 formed near the terminal end of the shaft 10and thereby axially lock the hub 22 on the shaft 10 (see FIG. 1). Asshown best in FIG. 2, the inner ends of the apertures 44 convergeinwardly to prevent the balls from falling therethrough when the hub 22is removed from the PTO shaft 10. The balls 42 are normally maintainedin their inward, locking position by means of a retaining ring 48axially slidable on the periphery of the hub portion 22 between a firstposition shown in FIG. 1, in which the ring 48 surrounds the balls 42and prevents their radial outward movement, and a second position shownin FIG. 5, in which the ring 48 is spaced rearwardly from the balls 42.A coil spring 50 acts between the rear side of the ring 48 and a flange52 on the hub portion 22 to bias the former toward its first position.

The operation of the mechanism described thus far is well known in theart. To insert the hub 22 on the shaft 10, the retaining ring 48 must bemoved axially against the force of the spring 50 to permit the balls 42to move radially outwardly to their unlocking position and to therebypermit passage of the shaft 10 through the hub 22. When the balls 42 arealigned with the groove 46 on the shaft 10, the retaining ring 48 mustthen be released for return to its initial position. In the past, thismanipulation of the retaining ring 48 was performed simultaneously asthe hub 22 was inserted on the shaft 10. The addition of thepreviously-described safety shielding to the power shaft 12 hassubstantially complicated this manipulation, however, and, since theshielding is rotatably mounted on the power shaft 12, its addition hasalso complicated the task of aligning the splines on the hub 22 withthose on the PTO shaft 10.

According to the present invention, a latch ring 54 is slidably mountedon the periphery of the hub 22 forwardly of the retaining ring 48 and isengageable therewith to move the ring 48 rearwardly against the urgingof the spring 50. The latch ring 54 comprises an axially extendingportion 56, a radially outwardly extending flange portion 58 at therearward end of the portion 56 and engageable with the front radial sideof the retaining ring 48, a radially inwardly extending projection 60 atthe forward end of the portion 56, and a semicircular, radially inwardlyextending flange portion 62 lying generally in the same plane as theprojection 60. Fixed to and extending outwardly from the portion 56 ofthe ring 54 is a cylindrical button 64. A collar 66 loosely surroundsthe latch ring 54, as well as the retaining ring 48, and includes aradial portion 68 slidably received by the hub 22, and an axial portion70 extending rearwardly in overlying relation with the forward end ofthe bell-shaped shield member 30 and having an aperture through whichthe outer end of the button 64 extends. A removable ring 72, engageablewith a circumferential groove in the forward end of the hub 22, isnormally operable to prevent removal of the collar 66 from the hub 22.It will be apparent from the structure described that the collar 66 andlatch ring 54 are rotatable as a unit relative to the hub 22, the collarthus serving as a shield member for the extreme forward end of the powershaft 12.

In the normal position of the latch ring 54, shown in FIGS. 1, 3, and 4,the projection 60 and flange 62 act as spacers to maintain the axialportion 56 of the latch ring in concentric relation with the hub 22.When moved axially rearwardly against the spring 50 and urged radiallyinwardly by means of the button 64, the projection 60 on the ring 54 isengageable with a circumferentially extending groove 74 formed in theperiphery of the hub 22 to lock the ring 54 axially relative to the huband to thereby lock the retaining ring 48 in its rearward position (seeFIG. 5). When so locked, the axial portion 56 of the latch ring 54 isdisposed eccentrically relative to the hub 22, as indicated in FIGS. 6

and 7, and is operative to prevent at least one of the balls 42 frommoving radially outwardly to its unlocking position. As the hub 22 isinserted on the PTO shaft 10, the beveled end portion 76 of the latterengages that ball and urges it outwardly against the latch ring 54,thereby disengaging the projection 60 from the groove 74 and releasingthe retaining ring 48. The ring 48 is then urged forwardly against theballs 42 by the spring 50 (see FIG. 8), the ring thus exerting a radialinward force on the balls which causes them to drop into the groove 46in the shaft 18 when the hub 22 is properly positioned thereon. Whe theballs 42 are positioned in the'groove 46, the retaining ring 48 is thenfree to move forwardly to its position surrounding the balls, shown inFIG. I.

As illustrated in FIGS. 6 and 7, a series of blind holes 78 are providedat equal intervals-along the groove 74 to receive the projection 60 onthe latch ring 54. When turned so that the projection 60 engages one ofthe holes 78, as shown in FIG. 7, the latch ring 54 and collar 66arerotatably locked to the hub 22, such that the latter can be rotatedin response to rotation of the former to align the splines in'the hub 22with those on the PTO shaft 10.

The sequence of operation of the shaft coupling mechanism will now bedescribed. Beginning with the mechanism in the position shown in FIG. 4,the button 64 is urged inwardly and the collar 66 "moved rearwardlyagainst the spring 50 until the projection 60 on the latch ring 54engages the groove 74 in the hub 22, thereby locking the retaining ring48 in its rearward po sition. If necessary to align the splines on thehub 22 with those on the shaft 10, the collar 66 and latch ring 54 canbe rotated relative to the hub 22 from the position shown in FIG. 6 tothat shown in FIG. 7, in which the projection 60 engages one of theenlarged portions 78 in the groove 74, thereby rotatably locking thecollar 66 to the hub 22. The hub 22 can then be rotated by means of thecollar 66 to align the splines on the hub with those on the PTO shaft.As the hub 22 is then axially inserted on the shaft 10, the beveled endof the latter contacts the balls 42 and moves them radially outwardlyagainst the latch ring 54, thereby releasing the latter from its lockedposition (see FIG. 8). Continued movement of the hub 22 brings the balls42 into alignment with the groove 46 on the shaft 10, whereupon theballs are urged inwardly into engagement with the groove by the spring50 and retaining ring 48. When the balls are in position in the groove46, the ring 48 is free to move forwardly to its position surroundingthe balls to axially lock the hub 22 on the shaft 10 (see FIG.

1). Removal of the hub from the PTO shaft is accomplished by merelypulling back on the collar 66 without depressing the button 64, therebymoving the ring 48 to its rearward position and permitting the balls 42to move radially outwardly to their unlocking position.

We claim:

l. he mechanism for coupling a first shaft having a recess near itsterminal end to a second, hollow, shaft adap'tedto axially receive saidfirst shaft, the mechanism including a plurality of circumferentiallyspaced locking elements supported on said second shaft and radiallymovable between an inner, locking position wherein said elements areengageable with the recess in said first shaft and are operable toprevent relative axial movement between said first and second shafts,and an outer, unlocking position wherein said elements permit suchrelative axial movement, a retaining member axially slidable on theperiphery of said second shaft between a first position wherein it isoperable to maintain said locking elements in their locking position,and a second position wherein it permits radial movement of said lockingelements to their unlocking position, and means acting between saidsecond shaft and said retaining member for biasing the latter axiallytoward its first position, the improvement comprising: a latch memberaxially slidable on the periphery of said second shaft and engageablewith said retaining member for moving the latter from its first to itssecond position against said biasing means, said latch member beingmovable radially inwardly within a recess in the periphery of saidsecond shaft to a latching position wherein it is axially locked againstsaid biasing means, said latch member being operable in its latchingposition to maintain said retaining member in its second position and tonormally maintain at least one of said locking elements in its inner,locking position; said first shaft being engageable with said at leastone locking element as it is axially inserted into said second shaft tomove said element radially outwardly against said latch member andthereby release the latter from its latching position.

2. The invention defined in claim l wherein said latch member comprisesa ring encircling said second shaft and having a radially extendingportion engageable with the recess in the periphery of said secondshaft, said latch member being eccentrically disposed relative tosaidsecond shaft when in its latching position.

3. The invention defined in claim 2 wherein the recess in the peripheryof said second shaft comprises a continuous, circumferentially extendinggroove.

4. The invention defined in claim 2 wherein said latch member includes aplurality of radially extending portions operative to maintain saidmember in concentric relation with said second shaft when said member isreleased from its latching position.

5. the invention defined in claim 2 including means on said second shaftengageable with said latch member when in its latching position forpreventing relative rotational movement between said second shaft andsaid latch member.

6. The invention defined in claim 5 wherein the recess in the peripheryof said second shaft comprises a continuous, circumferentially extendinggroove, said groove having a plurality of circumferentially spacedenlarged portions formed therein and engageable by the radiallyextending portion of said latch member to prevent relative rotationalmovement between said second shaft and said latch member.

7. The invention defined in claim 1 including a collar encircling saidlatch member and said retaining member and connected to the former foraxial and rotational movement therewith.

8. The invention defined in claim 7 including a portion-on said latchmember extending radially through an aperture in the wall of saidcollar. 1 9. The invention defined in claim 8 wherein the radiallyextending portion of said latch member extending through said collar,and the radially extending portion thereof engageable with the recess inthe second shaft are substantially radially aligned, the former portionserving as means for manually urging said latch member into itslatchingposition.

10. The invention defined in claim 7 wherein said latch member and saidcollar, when the former is released from its latching position, are freeto rotate relative to said second shaft.

11. The invention defined in claim 10 including a shield encircling saidsecond shaft and free to rotate relative thereto, said shield having aterminal end extending between said collar and said second shaft.

12. The invention defined in claim 1 wherein said latch member, whenreleased from its latching position, is free to rotate relative to saidsecond shaft.

13. The invention defined in claim 12 wherein the recess in theperiphery of said second shaft comprises a continuous, circumferentiallyextending groove.

14. In a mechanism for coupling a first shaft having a recess near itsterminal end to a second, hollow, shaft adapted to axially receive saidfirst shaft, the mechanism including a plurality of circumferentiallyspaced locking elements supported on the second shaft and radiallymovable between an inner, locking position wherein said elements areengageable with the recess in said first shaft and are operable toprevent relative axial movement between said first and second shafts,and an outer, unlocking position wherein said elements permit suchrelative axial movement, a retaining member axially slidable on theperiphery of said second shaft between a first position wherein it isoperative to maintain said locking elements in their locking position,and a second position wherein it permits radial movement of said lockingelements to their unlocking position, and means acting between saidsecond shaft and said retaining member for biasing the latter axiallytoward its first position, the improvement comprising: a latch memberaxially slidable on the periphery of said second shaft and operative tomove the retaining member to its second position against said biasingmeans; and means for axially locking said latch member on said secondshaft against said biasing means and thereby locking said retainingmember in its second position, said latch member being releasable fromits locked position in response to movement of at least one of saidlocking elements from its locking to its unlocking position, said firstshaft being operative to move at least one of said locking elements fromits locking to its unlocking position as said first shaft is insertedaxially into said second shaft.

15. The invention defined in claim 14 wherein said means for axiallylocking said latch member on said second shaft comprises a recess on theouter periphery of said second shaft adapted to receive said latchmemher, said member surrounding said locking elements in eccentricrelation with said second shaft when received by said recess, saidlocking elements being engageable with said ring and operable to removethe same from said recess as said elements are moved to their unlockingposition.

16. In a mechanism for coupling a first shaft having a recess near itsterminal end to a second, hollow, shaft adapted to axially receive saidfirst shaft, the mechanism including a plurality of circumferentiallyspaced locking elements supported on the second shaft and radiallymovable between an inner, locking position wherein said elements areengageable with the recess in said first shaft and are operable toprevent relative axial movement between said first and second shafts,and an outer, unlocking position wherein said elements permit suchrelative axial movement, a retaining member axially slidable on theperiphery of said second shaft between a first position wherein it isoperative to maintain said locking elements in their locking position,and a second position wherein it permits radial movement of said lockingelements to their unlocking position, and means acting between saidsecond shaft and said retaining member for biasing the latter axiallytoward its first position, the improvement comprising: a latch memberaxially slidable on the periphery of said second shaft and operative tomove the retaining member to its second position against said biasingmeans; and means for axially locking said latch member on said secondshaft against said biasing means and thereby locking said retainingmember in its second position, said latch member being releasable fromits locked position in response to axial insertion of said first shaftinto said second shaft.

17. Apparatus for coupling a first shaft having a recess formed in theperiphery thereof to a second, hollow shaft adapted to axially receivesaid first shaft, comprising: at least one locking element supported onsaid second shaft and movable radially between an inner lockingposition, wherein said element is engageable with the recess in saidfirst shaft and is operative to axially lock said first and secondshafts, and an outer unlocking position, wherein said element isdisengaged from said recess and permits relative axial movement of saidshafts; a retaining member axially slidable on said second shaft betweena first position wherein it overlies said locking element and isoperative to retain said element in its inner locking position, and asecond position wherein it permits movement of said element to its outerunlocking position; means acting between said second shaft and saidretaining member for biasing the latter toward its first position; and alatch member axially slidable on said second shaft and operative to movesaid retaining member from its first to its second position against saidbiasing means, said latch member being movable radially inwardly intoengagement with a recess in the periphery of said second shaft to alatching position wherein it overlies said locking element and isoperative to lock the retaining member in its second position, saidlatch member being releasable from its latching position in response tomovement of said locking element from its locking to its unlockingposition, said first shaft being engageable with said locking elementand operative to move said element from its locking to its unlockingposition as it is axially coupled to said second shaft.

18. A shaft coupling including a hollow shaft having a surface recessand a radial aperture extending through the wall thereof, a lockingelement radially movable in said aperture between an innermost lockingposition for engagement with an internal mating shaft and an outerunlocking position out of engagement with said internal mating shaft, aretaining member axially slidable on said hollow shaft between a firstposition maintaining said locking element in its locking position and asecond position permitting radial movement of said locking element toits unlocking position, biasing means axially biasing said retainingmember toward its first position, and a latch member axially slidable onthe periphery of said hollow shaft and engageable with said retainingmember for moving the latter from its first to its second positionagainst said biasing means, said latch member being shiftable radiallyto seat in said surface recess for axially locking it in radial relationto said locking element to retain said locking element in its innerlocking position.

19. Shaft coupling apparatus comprising: a hollow shaft having a surfacerecess; a locking element supported on said hollow shaft and movablebetween an inner locking po'sition for engagement with a mating shaftaxially received by said hollow shaft and an outer unlocking positionout of engagement with said mating shaft; a retaining member axiallymovable on said hollow shaft between a first position maintaining saidlocking element in its locking position and a secod position permittingradial movement of said locking element to its unlocking position;biasing means axially biasing said retaining member toward its firstposition; and a latch member axially movable on said hollow shaft andoperative to move the retaining member to its second position againstsaid'biasing means, said latch member being shiftable radially to seatin said surface recess in said hollow shaft for axially locking saidretaining member in its second position, said latch member radiallyoverlying said locking element when seated in said recess and beingdisengageable from said recess in response to movement of said lockingelement to its outer unlocking position, said mating shaft beingengageable with and operative to move said locking element to its outerunlocking position as said mating shaft is axially inserted into saidhollow shaft.

20. The invention defined in claim 19 wherein the surface recess in saidhollow shaft comprises a continuous, circumferentially extending groove,and wherein said latch member comprises a ring encircling said hollowshaft and having a radially extending portion engageable with saidgroove.

21. The invention defined in claim 19 including means for rotatablylocking said hollow shaft to said 'latch member when the latter isseated in said recess.

1. In a mechanism for coupling a first shaft having a recess near itsterminal end to a second, hollow, shaft adapted to axially receive saidfirst shaft, the mechanism including a plurality of circumferentiallyspaced locking elements supported on said second shaft and radiallymovable between an inner, locking position wherein said elements areengageable with the recess in said first shaft and are operable toprevent relative axial movement between said first and second shafts,and an outer, unlocking position wherein said elements permit suchrelative axial movement, a retaining member axially slidable on theperiphery of said second shaft between a first position wherein it isoperable to maintain said locking elements in their locking position,and a second position wherein it permits radial movement of said lockingelements to their unlocking position, and means acting between saidsecond shaft and said retaining member for biasing the latter axiallytoward its first position, the improvement comprising: a latch memberaxially slidable on the periphery of said second shaft and engageablewith said retaining member for moving the latter from its first to itssecond position against said biasing means, said latch member beingmovable rAdially inwardly within a recess in the periphery of saidsecond shaft to a latching position wherein it is axially locked againstsaid biasing means, said latch member being operable in its latchingposition to maintain said retaining member in its second position and tonormally maintain at least one of said locking elements in its inner,locking position; said first shaft being engageable with said at leastone locking element as it is axially inserted into said second shaft tomove said element radially outwardly against said latch member andthereby release the latter from its latching position.
 2. The inventiondefined in claim 1 wherein said latch member comprises a ring encirclingsaid second shaft and having a radially extending portion engageablewith the recess in the periphery of said second shaft, said latch memberbeing eccentrically disposed relative to said second shaft when in itslatching position.
 3. The invention defined in claim 2 wherein therecess in the periphery of said second shaft comprises a continuous,circumferentially extending groove.
 4. The invention defined in claim 2wherein said latch member includes a plurality of radially extendingportions operative to maintain said member in concentric relation withsaid second shaft when said member is released from its latchingposition.
 5. the invention defined in claim 2 including means on saidsecond shaft engageable with said latch member when in its latchingposition for preventing relative rotational movement between said secondshaft and said latch member.
 6. The invention defined in claim 5 whereinthe recess in the periphery of said second shaft comprises a continuous,circumferentially extending groove, said groove having a plurality ofcircumferentially spaced enlarged portions formed therein and engageableby the radially extending portion of said latch member to preventrelative rotational movement between said second shaft and said latchmember.
 7. The invention defined in claim 1 including a collarencircling said latch member and said retaining member and connected tothe former for axial and rotational movement therewith.
 8. The inventiondefined in claim 7 including a portion on said latch member extendingradially through an aperture in the wall of said collar.
 9. Theinvention defined in claim 8 wherein the radially extending portion ofsaid latch member extending through said collar, and the radiallyextending portion thereof engageable with the recess in the second shaftare substantially radially aligned, the former portion serving as meansfor manually urging said latch member into its latching position. 10.The invention defined in claim 7 wherein said latch member and saidcollar, when the former is released from its latching position, are freeto rotate relative to said second shaft.
 11. The invention defined inclaim 10 including a shield encircling said second shaft and free torotate relative thereto, said shield having a terminal end extendingbetween said collar and said second shaft.
 12. The invention defined inclaim 1 wherein said latch member, when released from its latchingposition, is free to rotate relative to said second shaft.
 13. Theinvention defined in claim 12 wherein the recess in the periphery ofsaid second shaft comprises a continuous, circumferentially extendinggroove.
 14. In a mechanism for coupling a first shaft having a recessnear its terminal end to a second, hollow, shaft adapted to axiallyreceive said first shaft, the mechanism including a plurality ofcircumferentially spaced locking elements supported on the second shaftand radially movable between an inner, locking position wherein saidelements are engageable with the recess in said first shaft and areoperable to prevent relative axial movement between said first andsecond shafts, and an outer, unlocking position wherein said elementspermit such relative axial movement, a retaining member axially slidableon the periphery of said second shaft between a fIrst position whereinit is operative to maintain said locking elements in their lockingposition, and a second position wherein it permits radial movement ofsaid locking elements to their unlocking position, and means actingbetween said second shaft and said retaining member for biasing thelatter axially toward its first position, the improvement comprising: alatch member axially slidable on the periphery of said second shaft andoperative to move the retaining member to its second position againstsaid biasing means; and means for axially locking said latch member onsaid second shaft against said biasing means and thereby locking saidretaining member in its second position, said latch member beingreleasable from its locked position in response to movement of at leastone of said locking elements from its locking to its unlocking position,said first shaft being operative to move at least one of said lockingelements from its locking to its unlocking position as said first shaftis inserted axially into said second shaft.
 15. The invention defined inclaim 14 wherein said means for axially locking said latch member onsaid second shaft comprises a recess on the outer periphery of saidsecond shaft adapted to receive said latch member, said membersurrounding said locking elements in eccentric relation with said secondshaft when received by said recess, said locking elements beingengageable with said ring and operable to remove the same from saidrecess as said elements are moved to their unlocking position.
 16. In amechanism for coupling a first shaft having a recess near its terminalend to a second, hollow, shaft adapted to axially receive said firstshaft, the mechanism including a plurality of circumferentially spacedlocking elements supported on the second shaft and radially movablebetween an inner, locking position wherein said elements are engageablewith the recess in said first shaft and are operable to prevent relativeaxial movement between said first and second shafts, and an outer,unlocking position wherein said elements permit such relative axialmovement, a retaining member axially slidable on the periphery of saidsecond shaft between a first position wherein it is operative tomaintain said locking elements in their locking position, and a secondposition wherein it permits radial movement of said locking elements totheir unlocking position, and means acting between said second shaft andsaid retaining member for biasing the latter axially toward its firstposition, the improvement comprising: a latch member axially slidable onthe periphery of said second shaft and operative to move the retainingmember to its second position against said biasing means; and means foraxially locking said latch member on said second shaft against saidbiasing means and thereby locking said retaining member in its secondposition, said latch member being releasable from its locked position inresponse to axial insertion of said first shaft into said second shaft.17. Apparatus for coupling a first shaft having a recess formed in theperiphery thereof to a second, hollow shaft adapted to axially receivesaid first shaft, comprising: at least one locking element supported onsaid second shaft and movable radially between an inner lockingposition, wherein said element is engageable with the recess in saidfirst shaft and is operative to axially lock said first and secondshafts, and an outer unlocking position, wherein said element isdisengaged from said recess and permits relative axial movement of saidshafts; a retaining member axially slidable on said second shaft betweena first position wherein it overlies said locking element and isoperative to retain said element in its inner locking position, and asecond position wherein it permits movement of said element to its outerunlocking position; means acting between said second shaft and saidretaining member for biasing the latter toward its first position; and alatch member axially slidable on said secoNd shaft and operative to movesaid retaining member from its first to its second position against saidbiasing means, said latch member being movable radially inwardly intoengagement with a recess in the periphery of said second shaft to alatching position wherein it overlies said locking element and isoperative to lock the retaining member in its second position, saidlatch member being releasable from its latching position in response tomovement of said locking element from its locking to its unlockingposition, said first shaft being engageable with said locking elementand operative to move said element from its locking to its unlockingposition as it is axially coupled to said second shaft.
 18. A shaftcoupling including a hollow shaft having a surface recess and a radialaperture extending through the wall thereof, a locking element radiallymovable in said aperture between an innermost locking position forengagement with an internal mating shaft and an outer unlocking positionout of engagement with said internal mating shaft, a retaining memberaxially slidable on said hollow shaft between a first positionmaintaining said locking element in its locking position and a secondposition permitting radial movement of said locking element to itsunlocking position, biasing means axially biasing said retaining membertoward its first position, and a latch member axially slidable on theperiphery of said hollow shaft and engageable with said retaining memberfor moving the latter from its first to its second position against saidbiasing means, said latch member being shiftable radially to seat insaid surface recess for axially locking it in radial relation to saidlocking element to retain said locking element in its inner lockingposition.
 19. Shaft coupling apparatus comprising: a hollow shaft havinga surface recess; a locking element supported on said hollow shaft andmovable between an inner locking position for engagement with a matingshaft axially received by said hollow shaft and an outer unlockingposition out of engagement with said mating shaft; a retaining memberaxially movable on said hollow shaft between a first positionmaintaining said locking element in its locking position and a secodposition permitting radial movement of said locking element to itsunlocking position; biasing means axially biasing said retaining membertoward its first position; and a latch member axially movable on saidhollow shaft and operative to move the retaining member to its secondposition against said biasing means, said latch member being shiftableradially to seat in said surface recess in said hollow shaft for axiallylocking said retaining member in its second position, said latch memberradially overlying said locking element when seated in said recess andbeing disengageable from said recess in response to movement of saidlocking element to its outer unlocking position, said mating shaft beingengageable with and operative to move said locking element to its outerunlocking position as said mating shaft is axially inserted into saidhollow shaft.
 20. The invention defined in claim 19 wherein the surfacerecess in said hollow shaft comprises a continuous, circumferentiallyextending groove, and wherein said latch member comprises a ringencircling said hollow shaft and having a radially extending portionengageable with said groove.
 21. The invention defined in claim 19including means for rotatably locking said hollow shaft to said latchmember when the latter is seated in said recess.